The present invention relates to a method of controlling sound reproduction of an enclosure mounted electrodynamic loudspeaker of a portable communication device and a corresponding sound reproduction assembly. The method of controlling sound reproduction comprises steps of applying an audio signal to a voice coil of the electrodynamic loudspeaker through an output amplifier to produce sound, detecting one of an impedance and admittance of the loudspeaker across a predetermined audio frequency range based on a detected voice coil current and voice coil voltage and determining a fundamental resonance frequency of the loudspeaker based on the detected impedance or admittance. The determined the fundamental resonance frequency of the loudspeaker is compared with a nominal fundamental resonance frequency of the loudspeaker representing a nominal acoustic operating condition of the electrodynamic loudspeaker and a change of acoustic operating condition of the electrodynamic loudspeaker is detected based on a frequency deviation between the determined fundamental resonance frequency and a nominal fundamental resonance frequency of the electrodynamic loudspeaker. The level of the audio signal may be attenuated in response to the frequency deviation meets a predetermined frequency error criterion.
The present invention relates to a method of controlling sound reproduction of an enclosure mounted electrodynamic loudspeaker of a portable communication device and a corresponding assembly for controlling sound reproduction of the enclosure mounted electrodynamic loudspeaker. The methodology preferably includes comparing a dynamically determined fundamental resonance frequency of the loudspeaker with a nominal fundamental resonance frequency of the loudspeaker representing a nominal acoustic operating condition of the electrodynamic loudspeaker. A change of acoustic operating condition of the electrodynamic loudspeaker is detected based on a frequency deviation between the determined fundamental resonance frequency and the nominal fundamental resonance frequency of the electrodynamic loudspeaker. The detection of the change of acoustic operating condition of the electrodynamic loudspeaker is highly useful in portable communication device for various purposes such as detection of acoustic leakage of a sealed enclosure in which the electrodynamic loudspeaker of the portable communication device is mounted. The electrodynamic loudspeaker is utilized for sound reproduction purposes in the portable communication device, e.g. as a receiver for producing sound by acoustic coupling to the user's ear, or as a loudspeaker for playing recorded music or for voice reproduction in teleconferencing applications. The change of acoustic operating condition of the electrodynamic loudspeaker can also be exploited to detect an acoustically blocked operating condition of the loudspeaker of the portable communication device and in response thereto adapt the sound reproduction of the loudspeaker in various ways as described below in additional detail.
Furthermore, it is of significant interest and value to provide a relatively simple method for detecting the change of acoustic operating condition of the electrodynamic loudspeaker and the underlying cause, e.g. enclosure leakage, to avoid excessive expenditure of computational resources of an application microprocessor of the portable communication device and/or other computational hardware resources.